fuel tank popping
Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=2689
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Topic: fuel tank popping
Posted By: Rusty_bits
Subject: fuel tank popping
Date Posted: 14 September 2011 at 7:24pm
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I was wondering if anyone could help me please, regarding my fuel tank which has suddenly started popping periodically while driving. It seems like the tank is pulling a vacume while driving and then popping periodically to relieve itself. Any thoughts on why this would all of a sudden just start happening, when I have been driving it for the last year everyday to work with no problems? regards, Mark ------------- regards, Rusty_bits |
Replies:
Posted By: Romeo
Date Posted: 14 September 2011 at 9:16pm
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There's supposed to be a system in place to vent the pressure (Can't remember it's name for the life of me now). If that system gets clogged, the tank will collapse as fuel gets pulled through. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 14 September 2011 at 10:11pm
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This might not answer your question directly, but the information in http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20110502-2-102797.html - This thread is quite informative.
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Posted By: Rusty_bits
Date Posted: 15 September 2011 at 6:46am
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Thank you for the replies. regards, Mark ------------- regards, Rusty_bits |
Posted By: Rusty_bits
Date Posted: 16 September 2011 at 4:54pm
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actually after alittle more research it actually seems like it is building up pressure, not a vacume as previously thought. ------------- regards, Rusty_bits |
Posted By: Romeo
Date Posted: 16 September 2011 at 5:36pm
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Hm, pressure usually comes from heat when it can't vent out. Vacuum is usually from running the pump (IE, driving) when the vacuum can't get out. ------------- Never shift into reverse without a back-up plan. |
Posted By: ARTIC-1
Date Posted: 17 September 2011 at 10:45am
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Every Fule tank ever made has a vent,unless backyard made! an if your tank is doing somthing strange? the first thing you check is the vent.even closed fuel cells have a pressure relief valve,its standard when you build them.Blow off is @ 7LB Max.you use a bidirectional pressure relief valve. DR,Fiero with the cap replace is most likely right.Try a vented cap Clay. cheers ------------- SNOW MAN 87-GT/AUTO-2.8_ WHITE 88-TTop/ Duke-2.5. RED |
Posted By: Patrick
Date Posted: 17 September 2011 at 11:25am
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No offense, but suggesting a vented gas cap be used in a system where the fuel tank vent is located elsewhere is pretty poor advice IMO. Fixing the problem instead of applying a band-aid solution would seem to be the wisest course of action here. I suspect having a vented gas cap on a vehicle that is not supposed to have one would also lead to an instant failure at AirCare. Venting gas fumes into the atmosphere instead of using the system designed to capture them (as shown in my previously mentioned link http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20110502-2-102797.html - Here ) is a definite no-no.
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ARTIC-1 wrote:Posted By: Romeo
Date Posted: 17 September 2011 at 12:28pm
He isn't mistaken, unless GM is an anomoly from literally every other manufacturer on the planet. Ford uses non-vented caps as well, but there is still a pressure where the cap will vent to prevent dangerous pressures in the tank (Between 10 and 12psi). Manufacturers realize that if the EVAP system gets clogged, then there's an inherit danger to sealing the system completely. That being said, I'd still focus on the EVAP system first, not the gas cap. The cap is a symptom, not a cause. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 17 September 2011 at 1:59pm
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Good point (as you previously mentioned when you stated, "a level where the cap will vent to prevent damage to the tank"). I wonder if that's what's occurring when Rusty_bits hears the popping. If so, it appears that the non-vented gas cap is indeed doing it's job by relieving the building pressure. Time to find out why the pressure is building up in the first place!
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Posted By: Romeo
Date Posted: 17 September 2011 at 2:09pm
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Precisely. I think the cap isn't the issue. I'm fairly certain the EVAP system is, seeing as how the EVAP system is normally what's used to regulate pressures inside the tank. That'd be where I'd start looking. ------------- Never shift into reverse without a back-up plan. |
Posted By: Indy
Date Posted: 17 September 2011 at 3:03pm
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I checked my 84 Duke fuel system, and hopefully yours is the same. There are 3 lines that connect the fuel tank to the engine compartment: fuel supply, fuel return, vent line to the canister. Presumably the problem is in the vent line. When I checked my spare set of fuel tank piping, the vent line is open in both directions, meaning that unless something is wrong, the fuel tank will not accumulate either vacuum or pressure. That line is connected to the canister and any vapours are vented to atmosphere through the charcoal filter. Even if the 2 vacuum lines that run from the canister to the engine are not functional, the fuel tank will still vent as it is suppoped to do so. I suggest that you disconnect the fuel tank vent line at the canister and check that air will pass to and from the fuel tank and that the canister is not blocked. Where the vent line enters the fuel tank it is fitted with a check valve that is open in the operating position. Presumably it is a safely feature to prevent a fuel leak through the vent if the car rolls. I guess that it is possible for the check valve to become frozen shut, but that is unlikely to occur. Cheers Gary |
Posted By: Rusty_bits
Date Posted: 18 September 2011 at 5:09pm
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Sorry for not commenting lately but I have been out. Thank you for all the comments when I get a chance to look at it I will start with the EVAP system. Regards Mark ------------- regards, Rusty_bits |
Posted By: Capt Fiero
Date Posted: 19 September 2011 at 12:10am
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I am really drunk at the moment, but here is my advice. Go to the evap system and vent all to atmosphere. Don't block any of them. you will find a single line Thait goes to the tank, leave that one to open air. I had that issue in my 88 due to a plugged Evap canister. Once open to air, it was fine. I find the evap can to be useless and have removed it on all my cars, eccept the 88 which I have left in tact, but still vented the tank to open atmosphere. ------------- Capt Fiero 88 Fiero GT 5spd V6 Eight Fifty Seven GT V8 5spd. |
Posted By: Romeo
Date Posted: 19 September 2011 at 3:15pm
Ssh. The AirCare... It's everywhere. They'll find out about that. ------------- Never shift into reverse without a back-up plan. |
Posted By: Patrick
Date Posted: 19 September 2011 at 4:09pm
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Yes, they will. And personally, I'm glad they're looking for it. Even without AirCare in the picture, I don't understand what the big deal is with replacing a defective EVAP (charcoal) canister on our cars. What would they charge for one at Pick-a-Part... five bucks, if that much? I see no down-side to retaining a properly functioning EVAP system the way it was designed and installed from the factory. It helps to keep raw gas fumes out of the air we breathe and it doesn't hurt engine performance at all. If some part of the EVAP system fails, simply replace the component. No need to rip it all out. ----------------------------------------------------------- Hmmmm.... on another note, it's interesting to see that three posts have mysteriously disappeared from this thread, two of which were by Tristan (Romeo) and myself which neither one of us deleted. A little "rewrite" of history, so it seems.
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